This invention relates to an improved heald control system, particularly suitable for multi-phase or travelling wave shedding looms. The invention which eliminates any cause of warp thread wear and which is of very low inertia, is of highly reliable operation at the high speeds required of modern textile looms.
Moreover, by allowing simple and rapid removal and installation of the entire heald assembly on the loom, said control system extremely facilitates the heald setting operation, which can now be done outside the machine, thus enabling this latter to continue to operate in the meantime with another harness (heald assembly). In both single-phase and multi-phase looms for weaving by weft and warp interweaving, the opening of the warp threads in order to form the shed into which the weft thread to be interwoven is inserted is effected by the vertical movement in opposite directions of two sets of healds. The healds include eyes through which pass said warp threads, one per eye. However, in the case of single-phase looms the moving of the healds in order to form a single shed is fairly simple, since all the healds of the two sets are moved simultaneously over the entire weaving height. This is no longer true in the case of multi-phase or travelling wave shedding looms in which the shed opening must take place in front of each of the weft inserters which move along the weaving zone, and must proceed in phase with these. There is therefore not a single open shed but instead a number of sheds equal to the number of weft inserters present in the weaving zone. Consequently the healds of each set must be arranged in the form of waves which travel synchronously with said weft inserters.
The state of the art already comprises various known types of heald control systems for effecting travelling wave opening, which is a characteristic of the multi-phase technology. These known control systems are all based on dividing the entire warp thread assembly and consequently the healds into a succession of small side-by-side sections. These sections behave like the frames of a conventional loom are moved mutually out of phase by a predetermined angle, so as to give rise to the required travelling wave shedding.
In a known construction, each of said sections is constituted substantially by two horizontal heald support arms which together with two vertical rods form a rigid rectangular frame of elongated shape.
However, such a design has considerable drawbacks. Firstly, the rigidity and consequently non-negligible weight of the frames lead to substantial inertial forces as a result of the reciprocating motion of the masses concerned, thus making this construction unsuitable for high-speed operation. In addition, the presence of the vertical rods of the aforesaid frames in the warp thread field creates interference with the warp threads and between the warp threads themselves in the zone surrounding said rods. This interference obstructs the crossing-over of said threads, therefore leading to damaging wear in the thread with consequent increase in the harmful and costly shut-downs of the loom due to thread breakage. Again, said vertical rods obstruct the weaving height, and reduce the maximum obtainable warp density.
In another known construction, said sections include a single vertical rod provided with small transverse arms suitably disposed for carrying the healds.
Although this known construction is of smaller mass and therefore smaller inertia, it however suffers from substantially the same drawbacks as the preceding construction.
The object of the present invention is to obviate the aforesaid drawbacks and thus provide a heald control system for a multi-phase loom which is of low energy consumption by virtue of its small inertia. The heald control system acts on the warp threads in such a manner as to enable them to undergo minimum possible wear during cross-over, and enables high warp densities to be obtained.